The present invention relates generally to wound sheet rolls, and, more specifically, to the manufacture thereof.
Sheet rolls are found in various forms including paper rolls used in adding machines, cash registers, Automated Teller Machines (ATMs), and fax machines for example. Each roll includes a sheet of paper wound around a center core. The core may be formed of paper, or plastic in a solid or honeycomb configuration.
Plastic cores are typically manufactured by extrusion, or may be individually molded. In extrusion production, tubular cores are extruded in logs of two or more unit cores and then precut to desired unit lengths. The logs are accumulated in batches and simultaneously cut into the unit cores using a gang saw. The length of the individual cores is therefore controlled by the accuracy of sawing the opposite ends thereof from the logs.
Each core must meet a suitable tolerance specification in length and diameter, for both the subsequent winding of paper thereon and use thereof in the appropriate machine for which it is produced. In order to wrap each core with paper, several cores, between thirty and forty for example, are coaxially mounted in end-to-end contact on a common mandrel or arbor in the form of a rod which extends through the bores thereof. The number of cores is determined by their individual length so that they may collectively extend within the full width of the corresponding supply paper roll. The paper is carried through a slitting and winding machine which simultaneously slits the paper into a number of ribbons corresponding to the number of cores for winding the ribbons on the individual cores on the run.
The slitting machine includes a plurality of female slitting knives in disk form which are axially aligned with the abutting ends of adjacent cores on the mandrel to effect respective parting planes between the opposite axial ends of each of the cores once they are wound with the paper. The knives are typically mounted on a common support, and are accurately spaced apart from each other using precision spacers. The wound paper rolls are then removed from the mandrel and separated, and typically undergo a pressing operation on each of the opposite two axial sides to ensure suitable flushness of the paper edges and the central core. The individual paper rolls may then be formed in suitable groups or packs and are typically wrapped in shrinkwrap plastic for subsequent delivery to the marketplace.
This method of production has been in commercial use for many years for producing large batches of paper rolls at significant speed. However, very small tolerances are required in manufacturing the individual cores and aligning them in the slitting machine to reduce undesirable manufacturing problems. Typical manufacturing tolerances are represented by plus and minus values which necessarily result in stack-up of the different tolerances where tolerances may accumulate and exacerbate alignment problems.
One common problem is the inter-leaving of adjacent sheet ribbons during the winding process which physically joins together adjacent wound rolls. This sometimes makes difficult, if not impossible, the breaking apart of the adjacent paper rolls upon removal from the mandrel. Similarly, individual cores may protrude from one end of the respective paper rolls and into an opposite end of an adjacent paper roll on the mandrel which also makes difficult the separation of the individual rolls upon removal from the mandrel. Core protrusion also increases the need for post-processing of the paper rolls to drive flush the core ends with the paper ends.
Yet another problem may occur at the beginning of the slitter winding process when the leading edge of the paper is bent 180xc2x0 in a tuck prior to being wound atop the core. These tucked tails are created by blowing with air the several leading edges of the ribbons for engaging a cooperating tucking bar which forms the tucked tails directly on the outer surface of the several cores. Excessive tolerance accumulation may also result in overlapping of the tucked tails which again renders difficult the separation of the final paper rolls from the mandrel after the winding process.
The very nature of the prior art gang sawing of unit cores from the core logs necessarily results in a corresponding tolerance in the length of the individual cores which is related to the initial length of the logs. A typical minimum tolerance in core length is about plus or minus 5 mils and increases as the log length increases. This is in contrast with the spacing tolerance between adjacent slitting knives which may be as little as about plus or minus 1.5 mils in view of the precision spacers used in mounting together the slitting knives.
Since the individual cores are merely arranged in abutting end-to-end contact on the cooperating common mandrel, the tolerances of each of the cores accumulates over the total number of cores mounted on an individual mandrel. Due to the random nature of manufacturing tolerances and accumulation thereof, excessive tolerance accumulation resulting in misalignment between the slitting knives and the core intersections can result, which occasionally leads to the undesirable problems mentioned above.
Accordingly, it is desired to eliminate or reduce excessive tolerance accumulation in the production of sheet wound cores for improving the manufacture thereof.
A segmented core includes a plurality of integral core segments defined by a respective separation slot in the outer surface thereof. A sheet is wound around the core in a plurality of layers and is slit at the slot to simultaneously wind respective sheet ribbons on the core segments to form individual rolls. The sheet slit is aligned with the core slot which allows the wound rolls to be broken apart at the slots.